There are many applications of mid- and far-infrared lasers, including inter alia trace-gas sensing, air pollution monitoring, medical devices (for diagnostics or treatment), optical communications, and spectroscopy. In most of these applications, high radiation intensity is an important requirement. Another typical requirement is that radiation emitted by a laser is to be appropriately collimated or projected. A frequent requirement for improving the performance of semiconductor lasers, especially those operating in mid- and far-infrared spectra, is to cool the lasers, often to cryogenic temperatures (below −100° C. or 170K). In view of these and other requirements, lasers are often used as components of larger optical systems, configured for optimal laser operation and optimal projection of the produced light.
Concerning the mid- and far-infrared semiconductor lasers, these lasers are attractive because they are, generally, cheaper as well as more compact and power-efficient than of other types, although their radiation intensity is not as high as of, for example, wavelength-shifted solid-state lasers. Examples of mid- and far-infrared semiconductor lasers are Quantum Cascade Lasers (QCLs), Interband Cascade Lasers (ICLs), and direct-bandgap antimonide lasers. These lasers may be pumped optically or electrically.
Various cooling and cryogenic cooling schemes for lasers have been developed. An example of a cryogenic cooling apparatus employing heat sink and diffuser plate for cooling small objects is described in U.S. Pat. No. 5,628,196.
For some particular applications, operation with more than one laser is needed; and all of these lasers may require a refrigerated environment. For example, U.S. Pat. No. 4,873,843 discloses a refrigerated environment for multiple laser sources and/or sensors which provides the same thermal conditions in a single cold-cycle refrigerator for the sensors and sources; and a mounting structure which comprises a cold-head assembly accommodating plural sensors or sources and positions them for radiation transfer with the ambient while they are held at consistent temperature relationships for efficient operation.